One hundred and twenty patients scheduled for major abdominal surgery under TEA combined general anesthesia were randomized in a double-blinded method to receive one of three different concentration study solutions in 8 ml of volume after the induction of anesthesia: 0.75% ropivacaine (60 mg), 0.375% ropivacaine (30 mg), or 0.2% ropivacane (16 mg).